Cracked flat roof repaired and waterproofed

With the introduction of the manually applied Purtop HA product, Mapei South Africa has extended its Purtop in situ polyuria membrane waterproofing system.

Commissioned to provide a solution for a badly cracked flat roof on a house in a Pretoria estate, Mapei South Africa suggested Purtop HA, a manually applied waterproofing product that was recently introduced as an extension of the company’s Purtop in situ polyuria membrane waterproofing system.

For the project, Mapei’s technical support team trained the selected contractor to become a Purtop HA approved applicator.

First, the cracks were ground open and a structural repair was carried out using Mapei Epojet LV. The existing substrate was then roughened with cup-brush grinders, cleaned, solvent wiped and then primed to ensure a sound mechanical bond for the waterproofing membrane.

The two-component Purtop HA kit was mechanically mixed and poured directly onto the touch-dry primed surface. Initially spread with a 5mm notch trowel to gauge the correct thickness, it was thereafter carefully smoothed to create an impressively neat, seamless finish.

Purtop HA A two-component, solvent-free formulation, Purtop HA has been designed for application by hand to form tough elastic waterproofing membranes on small to medium size flat roofs and terraces. It is also used to carry out repairs to surfaces that have been waterproofed with hybrid polyuria or pure polyuria membranes.

The product adheres extremely well to many different types of substrate after proper preparation to remove any oil, grease or dirt and, in the case of concrete and screeds, priming with Mapei Primer SN, followed by dusting with Quartz 0,5.

Once thoroughly mixed, Purtop HA stays workable for 20 minutes at about 23°C and can be applied easily and quickly to give a neat, seamless 2mm thick grey membrane that allows light foot traffic within 24 hours. The hardened product has very good resistance to alkalis, dilute acids and detergents, combined with excellent tensile (10N/mm2 in terms of DIN 53504) and tear strength (40N/mm2 according to ISO 34-1).

A complete waterproofing solution“In keeping with Mapei South Africa’s total solution approach, we offer a range of Mapei primers for different substrates, as well as preparation systems for less than ideal surfaces,” says Paul Nieuwoudt, Mapei South Africa’s product manager for building systems.

“These include cavity repair grouts and epoxy primers to speed up work when residual moisture levels in the substrate are higher than recommended and rust prevention epoxy primers for steel,” he says.

Over the past six years, Mapei South Africa’s technical service team has been introducing the local construction industry to the benefits of the advanced building technology additives, sealants, adhesives and concrete performance chemicals that are available from the international Mapei Group. Offering market-leading performance and handling advantages, Mapei’s 1 400 products are recognised throughout Europe, America and the Far East.